The present invention relates to an electronic device system which includes semiconductor integrated circuits, and which can detect a current consumption of the integrated circuits.
In an electronic device system which includes semiconductor integrated circuits, it is necessary to measure an electric current that passes through each integrated circuit. Therefore, the electronic device system includes current detecting circuits.
A conventional electronic device system which includes current detecting circuits is shown in FIG. 8. The electronic device system 800 comprises a plurality of integrated circuits 1 and a plurality of current detecting circuits. In FIG. 8, the current detecting circuits are ammeters 3. One integrated circuit 1 includes an internal circuit 5. This internal circuit 5 comprises any one of various circuits, such as a CPU, a microcontroller, a memory circuit, a logic circuit and so on.
A first terminal 5a of the internal circuit 5 is connected to a power voltage pad 1a which is provided with a power supply voltage VDD from a power supply. A second terminal 5b is connected to a GND pad 1b which is provided with a ground voltage GND.
The ammeter 3 is connected in series between the power voltage pad 1a and the power supply and measures an electric current passing through the internal circuit 5.
In the conventional electronic device system, for each internal circuit, a plurality of ammeters are located in order to measure an electric current passing through each internal circuit. Therefore, it is difficult to reduce the size of the electronic device system.
An object of the invention is to provide an electronic device system which allows for the size thereof to be reduced.
To achieve the object, according to one aspect of the invention, an amount of current which passes through a resistive element located between a power supply voltage and an internal integrated circuit is calculated on the basis of the power supply voltage and an voltage which occurs on an node between the resistive element and the internal circuit.
According to the present invention, in the electronic device system which includes a plurality of internal integrated circuits, a detecting circuit can be shared to measure an electric current passing through each internal integrated circuit. Therefore, it is possible to reduce the size of the electronic device system.